This invention relates generally to methods and apparatus for the collection and separation of liquids of different density (typically one of which is considered to be an undesirable contaminant of the other) and for the recovery of the less dense liquid. More specifically, the present invention has particular applicability to (but is not limited to) the clean-up of oil or other chemical spills from surface waters of bays, inlets, harbors, lakes, rivers, shorelines and offshore ocean ways.
There are numerous examples of contaminant spill clean-up apparatus and related techniques described in the patent literature. Representative patents include the following: U.S. Pat. Nos. 4,818,399; 4,203,842; 4,146,482; 3,862,040; 3,860,519; 3,815,751; 3,752,317; 3,741,391; 3,690,464; 3,642,140; 3,578,171; and 2,876,903.
The present invention seeks to improve over prior known apparatus and/or techniques as will be apparent from the description which follows.
The invention has for its principal object the provision of apparatus and associated methodology for clean-up of chemical or other contaminant spills of virtually any size in any type of waterway, and for substantially preventing and/or minimizing intrusion of waterborne contaminants onto shorelines, beaches or other land areas or inlets to water treatment plants or the like. To this end, apparatus is provided with intake characteristics capable of creating an "inflow" of liquids (oil/water in the principal example) at such high rates as to prevent and/or reduce the spill or dispersion of the spill while operating on an aqueous surface. The apparatus is also designed to recover the spilled contaminant. Thus, the apparatus is configured for collection and separation of, by way of example, oil and water, recovery of the oil, and discharge of the separated water back into the waterway.
The apparatus of this invention generally includes a system of one or more inlet openings sized and positioned to allow surface fluid liquids (water and surface oil) to flow into a corresponding number of free floating intake devices or catch basins, each connected by one or more flexible conduits to a main collection tank. In one arrangement, the intake is in the form of a continuous torus, with a radially outwardly facing, 360.degree. inlet opening. In another arrangement, the intake is in the form of a discontinuous torus, i.e., a plurality of separate arcuate segments arranged in a generally torus shape as described in the above identified co-pending application.
The flexible conduits extending between the intake and the collection tank not only act as gravity drains for carrying the oil/water to the main collection tank, but also serve an important passive function in that they divorce any rigidity between the catch basins and the main collection tank. Thus, it will be appreciated that as the main tank fills and takes on weight, it will sink to an approximate predetermined depth in direct relationship to its weight (which may vary within limits as it reaches an approximate state of equilibrium during continuous operation), but the catch basins will be unaffected due to the slack provided by the flexible conduits. As a result, the catch basins will achieve a consistent water line zero at the surface, independent of the continuously varying level of the main collection tank.
In a first exemplary embodiment, the main collection tank is a free floating structure which incorporates a hydrocarbon pump and associated siphon float device as described in greater detail below. The pump is utilized to transfer separated surface oil collected in the tank to an oil recovery storage facility on board a nearby vessel, or on land if the system is operating near a shoreline. The level of oil/water in the main collection tank is controlled by a pressurized gas, preferably air, introduced into the tank by means of a conduit extending from a source of pressurized air (e.g. a conventional compressor) to an inlet in the top wall of the tank. The compressor, like the oil storage facility, may be located on a nearby vessel or on land, depending on the deployment location of the system.
The top wall of the tank is also provided with a valve-controlled vent or standpipe which is open when the compressor is shut down, and closed when the compressor is activated. By selective actuation of the compressor and standpipe valve by means of level sensors within the tank, the oil/water level, the oil to water ratio and the thickness of the oil in the tank can be controlled as described further herein.
The main collection tank is preferably also provided with a water discharge or drain in the bottom wall of the tank to provide a further measure of level control, and to permit periodic purging of the tank.
The tank as described is further provided with a flotation collar, preferably urethane filled, for insuring flotation of the tank.
In addition to the enhanced ability to control the oil/water level in the tank, a further advantage of the above described system is that the pressurized air tends to flatten the oil/water surface in the tank, thereby quieting the surface action and further enhancing the oil recovery aspect of the system.
The above described apparatus may be operated as follows. With the standpipe open and the compressor shut down, oil/water enters the intake device or catch basin and flows downward into the main collection tank. Ingestion of oil/water will occur at an inflow rate and oil/water ratio dependent on intake system selection and on the maximum feed pressure (based upon a .DELTA.P determined by the vertical distance between the intake device and the level of liquid inside the separation tank).
When the level of oil/water reaches a first level sensor, the hydrocarbon pump is activated and begins pumping oil which has risen to the surface within the tank, to storage. The level of oil/water continues to rise and reaches a second level sensor which causes the standpipe valve to close and the compressor to feed pressurized air into the tank (while separated oil continues to be pumped out of the tank). During this time, the level within the tank is maintained below the surface level outside the tank, and the pressurized air reaches an equilibrium with the water head (the pressure difference caused by the level in the tank versus the surface level outside the tank) and thereby causes the inflow of oil/water to cease. A further increase in air pressure will force water out of the intake device, thereby lowering the level inside the tank. In an alternative arrangement, a water drain and associated pump may be located in the bottom of the tank for discharging water from the tank to not only lower the water/oil level in the tank, but also to increase the oil to water ratio in the tank. When the level in the tank drops to a third level sensor, the standpipe valve is opened and the compressor shut down, thereby permitting oil/water to again flow into the intake device and into the tank. The above described procedure is then repeated in an essentially continuous manner until the vessel capacity for oil storage is reached and/or until the spill is substantially removed from the waterway.
In a second exemplary embodiment of the invention, the main collection tank is located within a tanker or other vessel, below the water line, so that oil/water will flow under the influence of gravity from one or more freely floating intake devices as described above. In this regard, a single intake device may be provided which is continuous in form, surrounding the vessel. Other configurations, of course, may also be utilized including one or more intake devices extending along either side of the vessel. The size, shape and number of intake devices or catch basins will be determined by the capacity of the collection tank, as well as the particular type and location of the spill.
Aside from the inboard configuration, this second exemplary embodiment differs from the first described embodiment principally in that no hydrocarbon pump is required. Rather, a weir dam configuration is employed wherein a cylindrical ring is mounted concentrically within the tank establishing a radially outer chamber between the tank wall and the cylindrical ring. In this embodiment, the oil/water inlets are arranged to feed the oil/water to the inner chamber defined by the cylindrical ring so that when this chamber fills, the oil on the surface of the oil/water will spill over the upper edge of the cylindrical ring, or weir dam, and flow downwardly into the radially outer chamber to one or more headers which transfer the separated oil to storage tanks within the vessel.
As in the first described embodiment, the top wall of the inboard tank is provided with an inlet for compressed air as well as a valve controlled standpipe or vent. A viewing window or panel is also provided to aid the operator within the vessel in controlling the oil/water level within the tank. The bottom wall of the tank may be provided with a water drainage conduit incorporating a pump which further facilitates control of the oil/water level within the tank, and which may also be utilized as an emergency evacuation conduit and/or for purging the tank and intakes.
In operation, the inboard embodiment will ingest oil/water in the same manner as the first described embodiment.
As the oil/water fills to the weir height, the compressor will introduce air under pressure to equal the .DELTA.P pressure thereby maintaining the liquid level at a height desired above the weir for essential continuous flow of surface oil to storage. The air pressure will also modulate the surface way of action for smooth weir surface feed.
Air pressure may also be used to control the height or level of oil/water at the weir dam to increase, decrease or void flow over the weir. As already indicated, an observation panel or window will allow the operator to observe the liquid level as well as the thickness of oil film on the surface of the oil/water and to control the compressor to achieve the desired results. The operator may also periodically increase air pressure above the .DELTA.P head pressure to thereby purge the water and intake fluid until the oil surface thickness has reached a desired dimension. The air pressure can then be reduced to resume collection separation and recovery of the spilled oil.
In another exemplary embodiment of the invention, an arrangement is provided which is particularly adapted for use in the clean-up of spills adjacent a beach or shoreline. In this embodiment, the main tank is divided into a oil/water collection tank and a non-vented overflow tank, with the level in both tanks controlled by compressed air from a source which may be conveniently located on land. In this embodiment, oil/water enters the collection tank by means of an intake device of the type described above, and the level within the tank rises to the level of an overflow valve in an interior partition dividing the main tank. When the oil in the overflow tank reaches a predetermined level, the overflow valve along with the vent or standpipe valve and the air inlet valve in the collection, are closed, and air inlet valve in the overflow tank opened. Air under pressure is introduced into the overflow tank forcing the oil therein to a storage tank on land by means of any suitable conduit arrangement. As the oil level drops within the overflow tank, a switch shuts down the compressor and the valve actuation reversed to resume collection and separation as described above.
In another related embodiment, the separation tank itself may be located on land, with the intake device being the only waterborne components of the apparatus. In this arrangement, the intake device itself will incorporate a pump for pumping the oil/water to the separation tank. Otherwise, the separation technique is essentially the same as described above, with compressed air controlling the oil/water level within the tank.
In all of the above described embodiments, the utilization of gas under pressure to control levels within collection and/or overflow tanks enables close control over the operation and provides for enhanced collection, separation and recovery in a simple, efficient and low cost manner not previously possible with conventional systems.
Other objects and advantages of the invention will become apparent from the detailed description which follows.